File indexing completed on 2024-05-19 05:31:34

 /*
     SPDX-FileCopyrightText: 2023 Xaver Hugl <xaver.hugl@gmail.com>
 
     SPDX-License-Identifier: GPL-2.0-or-later
 */
 #include "colorspace.h"
 
 #include <qassert.h>
 
 namespace KWin
 {
 
 static QMatrix4x4 matrixFromColumns(const QVector3D &first, const QVector3D &second, const QVector3D &third)
 {
     QMatrix4x4 ret;
     ret(0, 0) = first.x();
     ret(1, 0) = first.y();
     ret(2, 0) = first.z();
     ret(0, 1) = second.x();
     ret(1, 1) = second.y();
     ret(2, 1) = second.z();
     ret(0, 2) = third.x();
     ret(1, 2) = third.y();
     ret(2, 2) = third.z();
     return ret;
 }
 
 QVector3D Colorimetry::xyToXYZ(QVector2D xy)
 {
     return QVector3D(xy.x() / xy.y(), 1, (1 - xy.x() - xy.y()) / xy.y());
 }
 
 QVector2D Colorimetry::xyzToXY(QVector3D xyz)
 {
     xyz /= xyz.y();
     return QVector2D(xyz.x() / (xyz.x() + xyz.y() + xyz.z()), xyz.y() / (xyz.x() + xyz.y() + xyz.z()));
 }
 
 QMatrix4x4 Colorimetry::chromaticAdaptationMatrix(QVector2D sourceWhitepoint, QVector2D destinationWhitepoint)
 {
     static const QMatrix4x4 bradford = []() {
         QMatrix4x4 ret;
         ret(0, 0) = 0.8951;
         ret(0, 1) = 0.2664;
         ret(0, 2) = -0.1614;
         ret(1, 0) = -0.7502;
         ret(1, 1) = 1.7135;
         ret(1, 2) = 0.0367;
         ret(2, 0) = 0.0389;
         ret(2, 1) = -0.0685;
         ret(2, 2) = 1.0296;
         return ret;
     }();
     static const QMatrix4x4 inverseBradford = []() {
         QMatrix4x4 ret;
         ret(0, 0) = 0.9869929;
         ret(0, 1) = -0.1470543;
         ret(0, 2) = 0.1599627;
         ret(1, 0) = 0.4323053;
         ret(1, 1) = 0.5183603;
         ret(1, 2) = 0.0492912;
         ret(2, 0) = -0.0085287;
         ret(2, 1) = 0.0400428;
         ret(2, 2) = 0.9684867;
         return ret;
     }();
     if (sourceWhitepoint == destinationWhitepoint) {
         return QMatrix4x4{};
     }
     const QVector3D factors = (bradford * xyToXYZ(destinationWhitepoint)) / (bradford * xyToXYZ(sourceWhitepoint));
     QMatrix4x4 adaptation{};
     adaptation(0, 0) = factors.x();
     adaptation(1, 1) = factors.y();
     adaptation(2, 2) = factors.z();
     return inverseBradford * adaptation * bradford;
 }
 
 QMatrix4x4 Colorimetry::calculateToXYZMatrix(QVector3D red, QVector3D green, QVector3D blue, QVector3D white)
 {
     const auto component_scale = (matrixFromColumns(red, green, blue)).inverted() * white;
     return matrixFromColumns(red * component_scale.x(), green * component_scale.y(), blue * component_scale.z());
 }
 
 Colorimetry Colorimetry::interpolateGamutTo(const Colorimetry &one, double factor) const
 {
     return Colorimetry{
         m_red * (1 - factor) + one.red() * factor,
         m_green * (1 - factor) + one.green() * factor,
         m_blue * (1 - factor) + one.blue() * factor,
         m_white, // whitepoint should stay the same
     };
 }
 
 Colorimetry::Colorimetry(QVector2D red, QVector2D green, QVector2D blue, QVector2D white)
     : m_red(red)
     , m_green(green)
     , m_blue(blue)
     , m_white(white)
     , m_toXYZ(calculateToXYZMatrix(xyToXYZ(red), xyToXYZ(green), xyToXYZ(blue), xyToXYZ(white)))
     , m_fromXYZ(m_toXYZ.inverted())
 {
 }
 
 Colorimetry::Colorimetry(QVector3D red, QVector3D green, QVector3D blue, QVector3D white)
     : m_red(xyzToXY(red))
     , m_green(xyzToXY(green))
     , m_blue(xyzToXY(blue))
     , m_white(xyzToXY(white))
     , m_toXYZ(calculateToXYZMatrix(red, green, blue, white))
     , m_fromXYZ(m_toXYZ.inverted())
 {
 }
 
 const QMatrix4x4 &Colorimetry::toXYZ() const
 {
     return m_toXYZ;
 }
 
 const QMatrix4x4 &Colorimetry::fromXYZ() const
 {
     return m_fromXYZ;
 }
 
 QMatrix4x4 Colorimetry::toOther(const Colorimetry &other) const
 {
     // rendering intent is relative colorimetric, so adapt to the different whitepoint
     return other.fromXYZ() * chromaticAdaptationMatrix(this->white(), other.white()) * toXYZ();
 }
 
 Colorimetry Colorimetry::adaptedTo(QVector2D newWhitepoint) const
 {
     const auto mat = chromaticAdaptationMatrix(this->white(), newWhitepoint);
     return Colorimetry{
         xyzToXY(mat * xyToXYZ(red())),
         xyzToXY(mat * xyToXYZ(green())),
         xyzToXY(mat * xyToXYZ(blue())),
         newWhitepoint,
     };
 }
 
 bool Colorimetry::operator==(const Colorimetry &other) const
 {
     return red() == other.red() && green() == other.green() && blue() == other.blue() && white() == other.white();
 }
 
 bool Colorimetry::operator==(NamedColorimetry name) const
 {
     return *this == fromName(name);
 }
 
 const QVector2D &Colorimetry::red() const
 {
     return m_red;
 }
 
 const QVector2D &Colorimetry::green() const
 {
     return m_green;
 }
 
 const QVector2D &Colorimetry::blue() const
 {
     return m_blue;
 }
 
 const QVector2D &Colorimetry::white() const
 {
     return m_white;
 }
 
 static const Colorimetry BT709 = Colorimetry{
     QVector2D{0.64, 0.33},
     QVector2D{0.30, 0.60},
     QVector2D{0.15, 0.06},
     QVector2D{0.3127, 0.3290},
 };
 
 static const Colorimetry BT2020 = Colorimetry{
     QVector2D{0.708, 0.292},
     QVector2D{0.170, 0.797},
     QVector2D{0.131, 0.046},
     QVector2D{0.3127, 0.3290},
 };
 
 const Colorimetry &Colorimetry::fromName(NamedColorimetry name)
 {
     switch (name) {
     case NamedColorimetry::BT709:
         return BT709;
     case NamedColorimetry::BT2020:
         return BT2020;
     }
     Q_UNREACHABLE();
 }
 
 const ColorDescription ColorDescription::sRGB = ColorDescription(NamedColorimetry::BT709, NamedTransferFunction::gamma22, 100, 0, 100, 100);
 
 ColorDescription::ColorDescription(const Colorimetry &colorimety, NamedTransferFunction tf, double sdrBrightness, double minHdrBrightness, double maxFrameAverageBrightness, double maxHdrHighlightBrightness, const Colorimetry &sdrColorimetry)
     : m_colorimetry(colorimety)
     , m_transferFunction(tf)
     , m_sdrColorimetry(sdrColorimetry)
     , m_sdrBrightness(sdrBrightness)
     , m_minHdrBrightness(minHdrBrightness)
     , m_maxFrameAverageBrightness(maxFrameAverageBrightness)
     , m_maxHdrHighlightBrightness(maxHdrHighlightBrightness)
 {
 }
 
 ColorDescription::ColorDescription(NamedColorimetry colorimetry, NamedTransferFunction tf, double sdrBrightness, double minHdrBrightness, double maxFrameAverageBrightness, double maxHdrHighlightBrightness, const Colorimetry &sdrColorimetry)
     : m_colorimetry(Colorimetry::fromName(colorimetry))
     , m_transferFunction(tf)
     , m_sdrColorimetry(sdrColorimetry)
     , m_sdrBrightness(sdrBrightness)
     , m_minHdrBrightness(minHdrBrightness)
     , m_maxFrameAverageBrightness(maxFrameAverageBrightness)
     , m_maxHdrHighlightBrightness(maxHdrHighlightBrightness)
 {
 }
 
 const Colorimetry &ColorDescription::colorimetry() const
 {
     return m_colorimetry;
 }
 
 const Colorimetry &ColorDescription::sdrColorimetry() const
 {
     return m_sdrColorimetry;
 }
 
 NamedTransferFunction ColorDescription::transferFunction() const
 {
     return m_transferFunction;
 }
 
 double ColorDescription::sdrBrightness() const
 {
     return m_sdrBrightness;
 }
 
 double ColorDescription::minHdrBrightness() const
 {
     return m_minHdrBrightness;
 }
 
 double ColorDescription::maxFrameAverageBrightness() const
 {
     return m_maxFrameAverageBrightness;
 }
 
 double ColorDescription::maxHdrHighlightBrightness() const
 {
     return m_maxHdrHighlightBrightness;
 }
 
 bool ColorDescription::operator==(const ColorDescription &other) const
 {
     return m_colorimetry == other.m_colorimetry
         && m_transferFunction == other.m_transferFunction
         && m_sdrGamutWideness == other.m_sdrGamutWideness
         && m_sdrBrightness == other.m_sdrBrightness
         && m_minHdrBrightness == other.m_minHdrBrightness
         && m_maxFrameAverageBrightness == other.m_maxFrameAverageBrightness
         && m_maxHdrHighlightBrightness == other.m_maxHdrHighlightBrightness;
 }
 
 static float srgbToLinear(float sRGB)
 {
     if (sRGB < 0.04045) {
         return std::max(sRGB / 12.92, 0.0);
     } else {
         return std::clamp(std::pow((sRGB + 0.055) / 1.055, 12.0 / 5.0), 0.0, 1.0);
     }
 }
 
 static float linearToSRGB(float linear)
 {
     if (linear < 0.0031308) {
         return std::max(linear / 12.92, 0.0);
     } else {
         return std::clamp(std::pow(linear, 5.0 / 12.0) * 1.055 - 0.055, 0.0, 1.0);
     }
 }
 
 static float nitsToPQ(float nits)
 {
     const float normalized = std::clamp(nits / 10000.0f, 0.0f, 1.0f);
     const float c1 = 0.8359375;
     const float c2 = 18.8515625;
     const float c3 = 18.6875;
     const float m1 = 0.1593017578125;
     const float m2 = 78.84375;
     const float powed = std::pow(normalized, m1);
     const float num = c1 + c2 * powed;
     const float denum = 1 + c3 * powed;
     return std::pow(num / denum, m2);
 }
 
 static float pqToNits(float pq)
 {
     const float c1 = 0.8359375;
     const float c2 = 18.8515625;
     const float c3 = 18.6875;
     const float m1_inv = 1.0 / 0.1593017578125;
     const float m2_inv = 1.0 / 78.84375;
     const float powed = std::pow(pq, m2_inv);
     const float num = std::max(powed - c1, 0.0f);
     const float den = c2 - c3 * powed;
     return 10000.0f * std::pow(num / den, m1_inv);
 }
 
 static QVector3D clamp(const QVector3D &vect, float min = 0, float max = 1)
 {
     return QVector3D(std::clamp(vect.x(), min, max), std::clamp(vect.y(), min, max), std::clamp(vect.z(), min, max));
 }
 
 QVector3D ColorDescription::encodedToNits(const QVector3D &nits, NamedTransferFunction tf, double sdrBrightness)
 {
     switch (tf) {
     case NamedTransferFunction::sRGB:
         return sdrBrightness * QVector3D(srgbToLinear(nits.x()), srgbToLinear(nits.y()), srgbToLinear(nits.z()));
     case NamedTransferFunction::gamma22:
         return sdrBrightness * QVector3D(std::pow(nits.x(), 2.2), std::pow(nits.y(), 2.2), std::pow(nits.z(), 2.2));
     case NamedTransferFunction::linear:
         return nits;
     case NamedTransferFunction::scRGB:
         return nits * 80.0f;
     case NamedTransferFunction::PerceptualQuantizer:
         return QVector3D(pqToNits(nits.x()), pqToNits(nits.y()), pqToNits(nits.z()));
     }
     Q_UNREACHABLE();
 }
 
 QVector3D ColorDescription::nitsToEncoded(const QVector3D &rgb, NamedTransferFunction tf, double sdrBrightness)
 {
     switch (tf) {
     case NamedTransferFunction::sRGB: {
         const auto clamped = clamp(rgb / sdrBrightness);
         return QVector3D(linearToSRGB(clamped.x()), linearToSRGB(clamped.y()), linearToSRGB(clamped.z()));
     }
     case NamedTransferFunction::gamma22: {
         const auto clamped = clamp(rgb / sdrBrightness);
         return QVector3D(std::pow(clamped.x(), 1 / 2.2), std::pow(clamped.y(), 1 / 2.2), std::pow(clamped.z(), 1 / 2.2));
     }
     case NamedTransferFunction::linear:
         return rgb;
     case NamedTransferFunction::scRGB:
         return rgb / 80.0f;
     case NamedTransferFunction::PerceptualQuantizer:
         return QVector3D(nitsToPQ(rgb.x()), nitsToPQ(rgb.y()), nitsToPQ(rgb.z()));
     }
     Q_UNREACHABLE();
 }
 
 QVector3D ColorDescription::mapTo(QVector3D rgb, const ColorDescription &dst) const
 {
     rgb = encodedToNits(rgb, m_transferFunction, m_sdrBrightness);
     rgb = m_colorimetry.toOther(dst.colorimetry()) * rgb;
     return nitsToEncoded(rgb, dst.transferFunction(), dst.sdrBrightness());
 }
 }